Nintendo first teased the existence of Metroid Prime 4 at E3 2017. Although the game was early in development, they thought it was important to let fans know it was in development. That may have been a mistake. Then in November Nintendo of America President Reggie Fils-Aime assured fans it was well in development with a release target in mind. That was definitely a mistake.
Today, Nintendo Senior Managing Executive Officer Shinya Takahashi shared an update on the game's progress, but it's probably not what you were expecting. According to Takahashi, Metroid Prime 4's development was deeply troubled, and Nintendo had to come to terms with the fact that it would not live up to the quality expected from the series.
As such, Nintendo has decided to scrap all their progress and start from scratch. Series producer Kensuke Tanabe will continue to be at the helm, but with a new development team... or rather an old one. Nintendo is returning to Retro Studios to develop the project this time. The Texas-based development team made the first three games in the series before branching off to make something new. Over four years later, Retro had still not announced anything prior to today.
Previously Nintendo had not announced who was handling development, but reports from reliable sources indicated it was Bandai Namco. It's unclear exactly what went wrong, but it was serious enough for Nintendo to pull the plug and change development teams. Unfortunately, this means we're now in for a long wait.